even strong players often fail to notice a threat. One of the major differences between orthodox and circular chess in practice is in the opening. In orthodox chess, opening theory has developed over several centuries, and the use of computer analysis has resulted in top level games frequently not deviating from known theory until the 20th move or beyond; in circular chess, there is virtually no opening theory, and consequently players are "on their own" from the first move. In orthodox chess, advancing the king's or queen's pawn are generally considered the best opening moves, as doing so attacks two key central squares, opens a diagonal to enable the development of a bishop, and, in the case of the king's pawn, the queen also. On a circular board these advantages are negated, as a king's or queen's pawn only attacks one square, and its advance only opens one square for the bishop. Some players advance the central pawns first anyway, while others prefer to advance the rooks' pawns in order to open lines of attack for the more powerful pieces; it is not known which move, if any, is objectively best. The different geometry of the square and circular boards creates considerable differences in endgame theory: three of the four "basic checkmates" on a square board (those with king and rook, king and two bishops, or king and bishop and knight against a lone king) rely on forcing the defending king into the corner of the board, and thus are impossible on a circular board since it doesn't have corners. The "basic mates" in circular chess are thus those with king and queen, king and rook and minor piece, or king and three minor pieces against a lone king. The greater tendency towards drawn endgames often results in the defender playing on in a position which would be considered cause for resignation on a square board. In one particular endgame, however, the circular board favours the attacker: with king and pawn against king, there is no stalemate defence (since it is impossible for the king to be trapped against a side of the board that the pawn is moving towards) and thus the only way for the defending king to draw is to capture the pawn before it can be either defended or promoted (otherwise the endgame is always a win). World Championship After experimenting with various possible layouts for